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Re: [ietf-smtp] Address transformations

2016-07-31 11:21:58
If by "resolving CNAMEs", you mean doing DNS resolution to
obtain A or MX records ...

No, I meant this part of RFC 1123:

      5.2.2  Canonicalization: RFC-821 Section 3.1

         The domain names that a Sender-SMTP sends in MAIL and RCPT
         commands MUST have been  "canonicalized," i.e., they must be
         fully-qualified principal names or domain literals, not
         nicknames or domain abbreviations.  A canonicalized name either
         identifies a host directly or is an MX name; it cannot be a

I think we all agree that was a mistake, and CNAMEs are fine in MAIL and RCPT and you shouldn't mess with them, but I can't find any place this advice has been explicitly deprecated.


PS: Even 5321 says the EHLO argument can't be a CNAME.

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